The present invention relates to a parallel-epipedal gable-topped bulk-material container made out of a multilayer plastic laminate and with its head sealed by a ridged seam, leaving two superimposed triangular folding tabs at the ends of the seam, whereby each tab is wrapped out and around a straight buckling edge on each side of the container and the container material has longitudinal and transverse or sloping scores for the edges of the body and floor or gable edges.
When the superimposed triangular folding tabs of a gable-topped container are wrapped around each transverse lateral buckling edge of the body, so much tension occurs in the outer layers of the ridged seam, which is also wrapped around, that what is called ridged-seam fracture will ensue transversely with respect to the seam. Ridged-seam fracture can be ascribed to some extent to the fibers of the laminate extending in the wrong direction (toward the buckling edge), to the thickness of the laminate (base with bonded-on polyethylene films and in special cases aluminum foil laminated in as an intermediate layer), to the particular sealing method, and to the superimposition of five laminations in the vicinity of the buckling edge.
Even if ridged-seam fracture occurs only on the outside of the container and accordingly does not directly impair its tightness, it is unacceptable because moisture can penetrate into the layers of the laminate over the long term, weakening the overall structure of the seal and of the container itself and eventually eliminating tightness. To prevent ridged-seam fracture or at least confine it within acceptable limits it has previously been necessary to acclimatize the container material (subject it to controlled temperature and humidity) at considerable expenditure to make it supple enough to make a container out of.
Gable-topped packages are made out of pre-scored blanks in a process that involves prefolding all the scoring and returning it to the original state of flatness before finally erecting the container. The prefolding leaves sharp-edged upthrusts along the scoring on the inside of the container, especially in blanks laminated with aluminum. The plastic coating on the blank accordingly becomes perforated when the ridged seam is constructed and laid flat, especially at the intersection between creases, where the longitudinal body scoring intersects with the transverse ridged-seam base line on the upper edge of the blank. The contents can then penetrate into the laminate while the container is being folded up and laid flat, contaminating both the inside of the container and the contents, which will no longer keep very long.